1. Field of the Invention
The present invention relates to a vacuum pipe for use in a synchrotron orbit radiation device for accelerating and storing charged particles, e.g., electrons, to generate synchrotron radiation light.
2. Description of the Related Art
FIG. 3 is a cross-sectional view of a vacuum pipe of a conventional synchrotron orbit radiation device described in, for example, pp 9 to 14 of Balker Review vol 14, No. 11.
In FIG. 3, a charged particle beam, e.g., an electron beam, is deflected with a deflection center 1 as a center thereof and proceeds on a circular path 2. A vacuum pipe body 3 is provided such that it surrounds this electron beam. The vacuum pipe body 3 is made of a thin bellow-type stainless steel.
A port portion cell 4 is interposed in the vacuum pipe body 3 in such a manner that it surrounds part of the electron beam path 2. The port portion cell 4 is also formed of a bellow-type stainless steel, like the vacuum pipe body 3, but is extended in the outer diameter direction of the path 2 relative to the vacuum pipe body 3.
The port portion cell 4 has a port 5 through which the synchrotron radiation emitted by the electron beam is introduced externally. The port 5 is opened in the tangential direction of the path 2.
In the thus-arranged vacuum pipe for use in the conventional synchrotron orbit radiation device, an accelerated electron beam emits synchrotron radiation in the tangential direction of the path 2 at the port portion 3 shown in FIG. 3. The generated radiation is externally introduced from the port 5.
If eddy currents are induced along the metallic wall of the vacuum pipe during the radial acceleration of the electron beam within the vacuum pipe, the deflecting magnetic field is adversely affected and the path 2 is made unstable. Most of such eddy currents flow along the path 2.
In the above-described vacuum pipe, since the vacuum pipe body 3 and the port portion cell 4 are formed by using a bellows made of a thin non-magnetic material, the resistivity of the wall portion along the path 2 is substantially increased, and generation of eddy currents is thus prevented.
In the above-described vacuum pipe for use in the conventional synchrotron orbit radiation device, the vacuum pipe body 3 and the port portion cell 4 are formed by using a welded bellows whose cross-sectional diameter changes in the direction of propagation of an electron beam. Therefore, as the electron beam passes, a wake may be formed on the wall portion. The wake adversely affects the deflecting magnetic field, like the eddy currents, and makes the path 2 unstable. Furthermore, the formation of a wake is increased at the port portion cell 4 because it has an increased cross-sectional diameter.